Ionic air purifiers are available in various sizes, such as floor standing or desktop units designed to clean the air within a room, to larger units designed to install into the heating and ventilation system of a residential or commercial building.
Ionic air purifiers pass an inlet air stream over one or more ionizing wires or an ionizing wire grid. The ionizing wires impart an electrical charge to the air flow, creating charged molecules known as ions, some of which eventually cling to airborne particles. In the case of air ionizers, the charged air is released as treated air. More sophisticated types of air purifiers include an electronic precipitator. Electronic precipitators add a set of oppositely charged particle collection plates, the plates having an electric charge opposite to that of the ionizing wires, and hence opposite to the charge of the particles reaching the plates. The oppositely charged collection plates attract the charged particles from the ionizing wires and due to the static charge, deposit the particles removed from the air stream onto the precipitator plates. In the precipitator type of air purifier, the precipitator plates must be cleaned at regular intervals of use to remove the accumulated particulate debris from the plates. A drawback of electronic ionic air purifiers is that all ionic purifiers generate some amount of ozone. Ozone is produced as a byproduct by the high voltage present at the ionizing wires as the high voltage converts oxygen into ozone.
Ionic air purifiers clean the air by electro statically removing both visible and invisible particles as small as 1/1000th (0.001) of a micron. These include allergy-causing pollens, exhaust and tobacco smoke, dust and even airborne bacteria.
An airplane passenger or crew cabin provides a unique environment compared to the conditions that most people encounter in their daily lives. The density of occupation in the passenger cabin is much higher than in any but the most crowded bars and theatres, and the available air volume is limited, as well as only a limited volume of make up air to replace stale cabin air. The relative humidity level in the aircraft cabin is generally lower than is encountered in buildings in any but the coldest parts of the world in winter due to the low temperatures outside the aircraft and low atmospheric pressure compared to the aircraft interior. In the cabin environment, as in any environment, thermal conditions as well as air pollutants and humidity levels affect the perceived air quality, and then there are the real air quality concerns of bacterial, particulate and chemical contamination either carried on board with the passengers or remaining in the aircraft fuselage and air vent passages from previous flights. The closed cabin and high density of occupation, together with the recirculation of the cabin air provides an efficient means of dispersing germs and viruses from sick passengers to those who are not yet infected but are now at risk within the airplane.
Aircraft air quality is a real problem for millions of travelers and thousands of airline employees. In recent years, a report from the National Research Council found evidence suggesting that a number of problems with the air circulating in passenger cabins may cause health problems. The report listed concerns that ozone levels in the cabin air may exceed regulatory standards, that oxygen pressure may not be adequate to protect passengers with pre-existing heart or respiratory diseases and that the air may be contaminated with traces of engine oil, hydraulic fluid, de-icing solutions, and even pesticides sprayed on international flights. Not surprisingly, those most affected are flight attendants and other crew members, some of whom have been complaining for years about headaches, blurred vision, dizziness, nausea and other health problems which they attribute to poor quality cabin air. Recently Alaska Airlines flight attendants won a $725,000 out-of-court settlement based on their contention that design flaws in two types of planes the airline flies had allowed chemical fluids to mix with cabin air and make them sick. However, the flight attendants lost a subsequent suit against the planes' manufacturers.
Even more recently and very illustrative of the dangers of aircraft cabin air is an article in Reuters News Service published on Apr. 13, 2006, wherein U.S. public health officials expressed concerned about an unexpected outbreak in mumps in the Midwest United States, and most notably the U.S. public health officials “are concerned that some people may have been infected (with mumps) on airline flights.” More than 600 people were reported sick in Iowa with mumps, a once common childhood disease that was believed to be eradicated with the use of measles, mumps and rubella vaccines in the 1950s and 60s. Quoted in the Reuters article, the United States Center for Disease Control (CDC) reports “This outbreak has spread across Iowa, and mumps activity, possibly linked to the Iowa outbreak, is under investigation in six neighboring states, including Illinois (four cases), Kansas (33 cases), Minnesota (one case), Missouri (four cases), Nebraska (43 cases), and Wisconsin (four cases).” Serious complications are associated with mumps, including meningitis, encephalitis, inflammation of the testicles or ovaries, inflammation of the pancreas and permanent deafness, among others. As with other viruses, mumps is transmitted by coughing and sneezing the virus contagions into the air where they are carried and later inhaled by other non-infected passengers. Of course, the high passenger density and closed confines of an aircraft passenger compartment together with the contaminant laden recirculation air system of the plane makes this all too easy. Mumps is “about as contagious as influenza”, the CDC said. Especially alarming is that those infected can pass along the virus to others for three days before they exhibit symptoms of the illness themselves, wherein they are not identifiable as ill before boarding the plane. The Reuters article notes that the CDC “said it was tracking two people who took nine flights in April (2006) and asked anyone showing symptoms of mumps to report to state health officials if they had been on the flights.” The CDC has begun use of a new system to track travelers who may pass viruses on air flights.
Other Researchers at the University of Pittsburgh Medical Center's Center for Biosecurity are raising concerns with the CDC seeking information on the specifics of the CDC's plans, if any, for the pre-emptive monitoring of international air flight travelers in the case of a pandemic of H5N1 bird flu, which is expected to eventually mutate to transfer easily human to human and has been likened by some in the medical profession to be the potential ‘Black Death’ of the 2000s.
A limitation of currently known ionic air purifiers is that they are relatively bulky in size and not capable of use onboard an aircraft, where from the above discussion, such a device is sorely needed. For an air purifier to be truly effective for the passenger, the purifier must directly connect to the passenger air vent so as to purify the air stream before it is directed into the passenger's personal breathing space. Conventional air purifiers are bulky, require substantial power to operate, and most importantly they are not directly connectable to an aircraft air vent to clean the ducted cabin air.
A primary means of air purification in ionic air purifiers is the chemical destruction of pollutants by ozone and the electrostatic precipitation of particles as the result of charging of the air stream in the ionizing grid.
A limitation of currently known ionic air purifiers is that they do not have a means to remove residual ozone generated by the ionic purifier from the purified air stream before it returns to the environment. Ozone is a known irritant and needs to be removed from the air stream to the greatest practical degree, especially within contained space of an aircraft.
Therefore, an airplane air purifier which is designed for direct installation over existing aircraft passenger air vent nozzles, a purifier which removes or destroys a wide variety of contaminants, particulate matter, viruses and bacteria, one which is safe to the user and the other passengers on the aircraft, one which provides a solution to the significant health problems associated with aircraft passenger cabin air as outlined in detail above, such an airplane air purifier would be useful and novel.